Antibacterial efficacy of facile cyanobacterial silver nanoparticles inferred by antioxidant mechanism.

Nanoparticles (NPs) have gained importance in technological advances owing to their user friendly enhanced and efficient physical, chemical, and biological characteristics compared to their bulk counterparts. Biological synthesis of NPs by using a microorganism, enzymes, or plant extracts offers a greener and eco-friendly approach besides many advantages over physical or chemical approaches. This study reports the biosynthesis of silver nanoparticles (AgNPs) using Nostoc muscorum NCCU 442 aqueous extract as the reducing and capping agent for AgNPs synthesis. The synthesized nanoparticles were characterized by UV-VIS spectrum, SEM, EDS, TEM, AFM, DLS and XRD. Results showed distinguishing polycrystalline nature of synthesized AgNPs with surface plasmon significant band in the size range of 6-45nm with average 30 size nm. FT-IR study revealed the role of secondary metabolites present in aqueous extract for the synthesis of AgNPs. Biological activities of purified AgNPs as antioxidant and antibacterial potential showed the highest antibacterial activity against Staphylococcus aureus MTCC 902.

Morphological and comparative genomic analyses of pathogenic and non-pathogenic Fusarium solani isolated from Dalbergia sissoo.

Sissoo or shisham (Dalbergia sissoo Roxb.) is one of the finest wood of South Asia. Fusarium solani is a causal organism of sissoo wilt, decline, or dieback. It is also a potential causal organism associated with other valuable tree species. Thirty-eight Fusarium isolates including 24 F. solani and 14 Fusarium sp., were obtained in 2005 from different geographical locations in India. All 38 (18 pathogenic and 20 non-pathogenic) isolates were characterized for genomic analysis, growth behaviour, pigmentation and sensitivity to carbendazim. Based on growth pattern, growth rate, pigmentation and sensitivity to carbendazim, all 38 isolates showed a wide range of variability, but no correlation with pathogenicity or geographical distribution. Three techniques were used for comparative genomic analysis: random amplified polymorphic DNA (RAPD); inter simple sequence repeats (ISSR); and simple sequence repeats (SSR). A total of 90 primers targeting different genome regions resulted a total of 1159 loci with an average of 12.88 loci per primer. These primers showed high genomic variability among the isolates. The maximum loci (14.64) per primer were obtained with RAPD. The total variation of the first five principal components for RAPD, ISSR, SSR and combined analysis were estimated as 47.42, 48.21, 46.30 and 46.78 %, respectively. Among the molecular markers, highest Pearson correlation value (r = 0.957) was recorded with combination of RAPD and SSR followed by RAPD and ISSR (r = 0.952), and SSR and ISSR (r = 0.942). The combination of these markers would be similarly effective as single marker system i.e. RAPD, ISSR and SSR. Based on polymorphic information content (PIC = 0.619) and highest coefficient (r = 0.995), RAPD was found to be the most efficient marker system compared to ISSR and SSR. This study will assist in understanding the population biology of wilt causing phytopathogen, F. solani, and in assisting with integrated disease management measures.

Sequence Analysis and Comparison of 16S rRNA, 23S rRNA and 16S/23S Intergenic Spacer Region of Greening Bacterium Associated with Yellowing Disease (Huanglongbing) of Kinnow Mandarin.

High incidence (up to 40%) of symptoms of yellowing and yellow mottling was observed in 5-8 years old orchards of kinnow mandarin {Citrus reticulate Balanco ('King' × 'Willow mandarin')} in the Punjab state of India during a survey in January 2007. These symptoms are often confused with nutrient deficiency and other stress related disorders. However, a greening bacterium has been attributed to cause the disease. The disease was graft transmissible and sequencing of 16S rRNA, 16S/23S intergenic spacer region and 23S rRNA of the greening bacterium associated with yellowing disease in kinnow mandarin confirmed it to be Candidatus Liberibacter asiaticus ('Ca L. asiaticus') showing maximum identity of 95.9% with 'Ca L. asiaticus' from USA and Brazil in 16S rRNA. The study indicates definite association of 'Ca L. asiaticus' with yellowing/chlorotic mottling symptoms of greening disease of kinnow mandarin in Punjab state of India.

Evidence of the Association of Radish leaf curl virus with Tobacco Yellow Leaf Curl Disease in Bihar, India.

A new disease of tobacco with characteristic mild leaf curl and yellowing symptoms was observed in 2007 in commercial plantings in Pusa, Bihar, India. A begomovirus and a betasatellite were found associated with the disease. The associated begomovirus was identified as a strain of Radish leaf curl virus (RaLCV) based on nucleotide sequence of the viral genome (2,761 nucleotides; EU194914). The betasatellite (HQ180397) associated with TbYLCD was identified as a variant of Chilli leaf curl betasatellite (ChLCB). Recombination events were detected both in the RaLCV and ChLCB sequences. This is the first report of yellow leaf curl disease of tobacco, and the association of RaLCV with a disease of tobacco.

Molecular characterization of Tobacco leaf curl Pusa virus, a new monopartite Begomovirus associated with tobacco leaf curl disease in India.

Leaf curl disease of tobacco (TbLCD) is endemic in India. A monopartite Begomovirus, a betasatellite and an alphasatellite were found associated with the disease in Pusa, Bihar. The DNA-A of the Begomovirus associated with TbLCD in Pusa, Bihar was found to comprise of 2707 nt with a typical Old World begomovirus-like genome organization. The full-length sequence of DNA-A [HQ180391] showed that the Pusa isolate is a newly described member of the genus Begomovirus, as it had <89% sequence homology with DNA-A of all the known begomoviruses. The isolate is tentatively named as Tobacco leaf curl Pusa virus [India:Pusa:2010]. The betasatellite (HQ180395) associated with TbLCD in Pusa was identified as a variant of Tomato leaf curl Bangladesh betasatellite [IN:Raj:03], with which it shared 90.4% sequence identity. The alphasatellite (HQ180392) associated with the disease had highest 87% nucleotide sequence identity with Tomato leaf curl alphasatellite. The Begomovirus, betasatellite, and alphasatellite associated with TbLCD in Pusa, Bihar, India were found to be recombinants of extant begomoviruses, betasatellites and alphasatellites spreading in the Indian sub-continent and South-East Asia.